1. Field of Invention
The present invention relates to a multi-phase signals generator and a voltage-controlled oscillator thereof.
2. Description of Related Art
In today's technology, voltage-controlled oscillators (VCOs) can be divided into three types, such as Colpittis oscillator, Hartely oscillator and Cross-couple oscillator. Most of the VCOs archive basic oscillation function by a resonant circuit composed of inductors and capacitors. The VCOs always be used in a phase lock loop (PLL) circuit, and in the presupposition of green power design, a power consumption of the PLL circuit is the most important point for designer. That is, it is the most important topic to archive a voltage-controlled oscillator with low power consumption in the design of the PLL circuit.
In the other way, with the progress of communication industry, integrated circuits (IC) have been widely applied in wireless communication. Such as that, a multi-phase signal generator (such as a quadrature-phase signal generator) comprising voltage-controlled oscillators be used. That is, the VCOs play an important role in modern communication systems. As the frequency up- and down-conversion is mainly performed by the mixers at the front electrode of the VCOs and the transmitter/receiver, the noise of the VCOs will influence the noise level of the entire transceiver. Therefore, it is an important subject how to reduce the phase noise of the VCOs.